Here is a guide to install Cube 2: Sauerbraten on Ubuntu 13.04. You can install Cube 2: Sauerbraten using the Ubuntu Software Center.
Cube 2: Sauerbraten is a free multiplayer & singleplayer first person shooter, the successor of the Cube FPS. Much like the original Cube, the aim of this game is fun, old school deathmatch gameplay and also to allow map/geometry editing to be done cooperatively in-game. Visit the Cube 2: Sauerbraten Homepage.
To install Cube 2: Sauerbraten click on the link below
Click to install Cube 2: Sauerbraten
When the software center is opened click on the Install button and enter your password to authenticate the installation. When Cube 2: Sauerbraten is installed you can close the software center, to start Cube 2: Sauerbraten press the SuperKey and type: sauerbraten
How to open the apt link? Read this article.